which may or may not reflect your candidate list, depending on what exclusions you made between the time you solved for your last cell and created the image.

I don't see a way to directly place a 9 in the suggested cell from this position. A 9 does eventually go there, but there are some intermediate steps that need to be taken before that happens.

The candidate list shows a naked pair in column 8 and a naked triple in row 8. Once those exclusions are mad there is a naked triple in column 4, which leads to a naked triple in row 3. Then a naked pair in box 2 is revealed, which leads to the reduction of the candidates in r2c6 to only a 6, which, when placed, leaves 9 as the only candidate in r1c4, which solves the puzzle to where only single placements are needed to the end.

After eliminating {6, 9} in r3c4, r3c5 & r3c6 we see that the "9" at r1c4 is unique in the top center 3x3 box, that "2" is the sole candidate for r1c5, and that the "6" at r2c6 is also unique in the top center 3x3 box. dcb

The candidate list shows a naked pair in column 8 and a naked triple in row 8. Once those exclusions are mad there is a naked triple in column 4, which leads to a naked triple in row 3. Then a naked pair in box 2 is revealed, which leads to the reduction of the candidates in r2c6 to only a 6

Actually, I think you missed out that before that, you have to put a 2 in r1c5 (correct me if i'm wrong?), but thanks. Still, it leaves the question as to why TDS's hint machine gave me the 9 for the original problem. I wonder if you can directly place that number somehow.

You are correct. After making the exclusions from the naked pair in box 2, r1c5 has only 2 as a possibility. Once played, that leaves r2c6 with only 6 and when that is played, then r1c4 has only 9.

David's post above explains how the 9 can be directly placed in r1c4, without need to do all the stuff I outlined, which I totally missed. I've always found hidden pairs are usually harder to spot than even naked quads.